Generally, a hydraulic excavator as a construction machine is largely constituted by an automotive lower traveling structure, an upper revolving structure which is swingably mounted on the lower traveling structure, and a working mechanism liftably mounted on the front side of the upper revolving structure.
The upper revolving structure is largely constituted by a revolving frame which forms a support structure; an engine provided on the rear side of the revolving frame to drive a hydraulic pump; a floor member provided on the revolving frame by being located on the front side of the engine, a rear side of which serves as an operator's seat mounting section for mounting an operator's seat, and a front side of which serves as a footrest section on which an operator rests his or her feet; a cab box provided so as to cover the surroundings and the upper side of the floor member to form an operating room above the floor member; and an air conditioner for supplying conditioned air to the operating room so as to improve the working environment of the operating room.
Here, the air conditioner is formed by connecting an outdoor unit on the engine side and an indoor unit on the floor member side by means of refrigerant pipes. The outdoor unit on the engine side is configured by including a condenser which is located midway in the refrigerant pipes and cools the refrigerant by the cooling air generated by a cooling fan of the engine. The indoor unit on the floor member side is configured by including a fan for generating a flow of air directed toward the operating room, as well as an evaporator which effects heat exchange at the time of expansion of the compressed refrigerant and cools the air generated by the fan and/or a heater core for heating through which engine cooling water circulates.
Meanwhile, among hydraulic excavators, there are small-sized hydraulic excavators called mini excavators which are suitable for operation in narrow work sites and in this small-sized hydraulic excavator, the upper revolving structure is formed to be small so as to be able to revolve even in narrow places.
In the small-sized hydraulic excavator, since the operating room is narrow, the indoor unit is disposed at the operator's foot. Namely, a large opening is provided in a footrest section of a floor member, and a bottomed box-shaped tray which is downwardly recessed is mounted in this opening. The indoor unit is disposed in this tray, and the upper side of the indoor unit is arranged to be covered with a cover (Patent Document 1).